If you have already submitted the application and it is being processed by the Pakistan VO, then CIC will not move your file to the UK.
If you have not yet submitted your application then you can request that London by your VO but only if you are already in London and have been admitted into the UK for at least a year. (You cannot request the UK as your VO if you are still in Pakistan. You must already be living in the UK.) Note that if you request London as your VO the file cannot be moved. This means that if an interview is required it will be held in London and the passport will also need to be send there for visa issuance. Will you be able to easily re-enter the UK after your year long stay in the UK is over? If the processing of your application exceeds your stay there and an interview is requested after you have left London, your wife will have to be able to re-enter the country to attend the interview or your application will be abandoned.
